How the hell do I actually write a sentinel class for a doubly-linked list?

So I'm in a compsci class (and switching to an English major after this summer session, because 1 suicide attempt a week thanks to stress is no way to live my life) and our current assignment centers around writing a sentineled doubly-linked list.In a wonderfully fucked turn of events, we were never actually taught how to do that, and so here I am. I understand how a linked list works for the most part, I'm just having trouble getting the initial construction of the sentinel nodes off the ground.Can anyone give me a hand here? via /r/learnpython http://ift.tt/2scQH5G